Platelet-venturi carburetor for combustion engine

ABSTRACT

A carburetor for combustion engines having a large number of small venturis to accomplish atomization, varporization and mixing of the fuel with air. The venturis are formed by an assembly or stack of platelets having fine orifices and complex channel shapes defined therein. The fuel can be either aspirated into the venturis by the difference in static pressure between the venturis and the fuel feed source, or it can be injected under pressure. The fine orifices produce droplets significantly smaller than prior art devices, and thus result in more rapid vaporization, finer atomization and better dispersing and mixing of the fuel-air mixture.

United States Patent [191 Kors et al.

451 Oct. 21, 1975 1 PLATELET-VENTURI CARBURETOR FOR COMBUSTION ENGINE[73] Assignee: Aerojet-General Corporation, El

Monte, Calif.

22 Filed: Feb. 25, 1974 21 App1.N0.:445,511

[52] US. Cl. 261/23 A; 60/3974 R; 239/555; 261/118 [51] Int. C1. F02M19/10; F02C 3/24 [58] Field of Search 239/555; 261/118, 23 A, 261/23 R,41 C; 60/3974 R, 39.74 A

[56] References Cited UNITED STATES PATENTS 2,484,123 10/1949 Scherl239/555 2,677,231 5/1954 Cornelius 1 60/282 2,713,894 7/1955 Sage239/555 2,735,664 2/1956 Gamble. 261/41 C 2,783,981 3/1957 Briggs 261/41C 3,269,666 8/1966 Leeuw 239/555 3,585,800 6/1971 Kuntz et al. 60/39663,612,397 10/1971 Pearson 239/555 3,618,319 9/1971 Kydd 1. 60/3974 R3,722,216 3/1973 Bahr et al. 60/3974 R 3,819,321 6/1974 Witt 60/3974 APrimary Examiner-Tim R. Miles Attorney, Agent, or FirmJohn L. McGannon;Marvin W. Murray [57] ABSTRACT A carburetor for combustion engineshaving a large number of small venturis to accomplish atomization,varporization and mixing of the fuel with air. The venturis are formedby an assembly or stack of platelets having fine orifices and complexchannel shapes defined therein. The fuel can be either aspirated intothe venturis by the difference in static pressure between the venturisand the fuel feed source, or it can be injected under pressure The fineorifices produce droplets significantly smaller than prior art devices,and thus result in more rapid vaporization, finer atomization and betterdispersing and mixing of the fuel-air mixture,

18 Claims, 3 Drawing Figures U.S. Patent Oct. 21, 1975 Sheet 1 of23,914,348

Sheet 2 0f 2 U.S. Patent Oct. 21, 1975 PLATELET-VENTURI CARBURETOR FORCOMBUSTION ENGINE BACKGROUND OF THE INVENTION This invention relates tocarburetor or burner devices for external or internal combustionengines.

The duel requirements of lower allowable combustion exhaust emissionlevels established by Government and high combustion efficiency requiredby industry impose design criteria which state of the art internal orexternal combustion engines cannot meet. The platelet-venturi carburetorherein described will provide the carburetion capability for an externalcombustion engine to meet the anticipated emission and performancecriteria.

The platelet-venturi carburetor will provide fuel metering, fineatomization and vaporization, and premixing of the vaporized fuel withthe air. Mixing is accomplished on a fine enough scale that mixturegradients will not occur in the combustor. The platelet-venturicarburetor provides such finely atomized and vaporized fuel mixturesthatdroplet sizes do not exceed 20 microns. It has been established thatdiffusion droplet burning with its inherent near stoichiometrictemperature flame front and local mixture ratio maldistributions whichpermit near stoichiometric combustion locally are major factors in theproduction of excessive N Ox emissions. The fine vaporization anduniform mixing provided by the platelet-venturi carburetor will thussignificantly reduce the NOx emission in external combustors.

The combustion preparation requirements, namely, vaporization andpremixing, must be effected without allowing chemical reaction to occurwithin the venturi. Consequently, the platelet-venturi carburetorincludes a flame quench capability to prevent flashback and reactionwithin the carburetor itself.

SUMMARY OF THE INVENTION The platelet-venturi carburetor device isbasically a carburetor which employs the venturi principle for fuelinjection, atomization and mixing. The platelet-venturi carburetoractually consists of hundreds of small venturis which provides superioratomization and mixing characteristics.

The conventional carburetor throttles by controlling the mixture downstream of the venturi. The plateletventuri carburetor is throttled bycontrolling the speed of the blower which provides the flow of airtherethrough. Fuel is introduced into the venturis at some pointupstream or at the throat (i.e. point of minimum cross-sectional area).The exact point of injection is determined by required mixture ratiocontrol over the throttle range. The fuel can be either aspirated intothe venturi by the difference in static pressure between the venturi andthe fuel feed source, or it can be injected under pressure. Generally,aspiration of the fuel is preferred.

The large velocity difference (approximately 500 to 1000 feet persecond) between the air and fuel causes the fine atomization anddispersion of the fuel droplets. Lateral pressures within the diffuserfurther acts to disperse the droplets such that a uniform mixture ofvaporized fuel and air is produced at the venturi exit. Flame quenchingis provided by dimensioning the venturi flow sections smaller than thequench distance.

The capability of the platelet-venturi carburetor to produce fine scaleatomization and mixing is a direct result of the platelet design and thephotoetch fabrication process which allows precise location of theextremely fine orifices and complex channel shapes. These are the keyfeatures which permit the plateletventuri carburetor approach toovercome the present carburetor design inadequacies. The fine orificesproduce small droplets and hence more rapid vaporization, which leads tothe complete combustion in short lengths required for low NOx emissionlevels. The orifices, being small, can be packed very close together,thus, improving heat transfer consideration conditions which effectburner face cooling and droplet vaporization. The precise location ofeach orifice and a large quantity of elements per unit area result inexcellent mass and mixture ratio control across the burner face. Thelack of restrictions on distribution complexity due to the photoetchtechnique permits flexibility of the design to meet a wide varity ofshapes and envelope requirements.

Further reduction in the emission levels can be achieved by completevaporization of the fuel within the platelet-venturi carburetor. Theheat transfer necessary to achieve complete vaporization of the fuel canbe either by conduction through the heated platelets or by direct mixingof the exhaust gases with the fuel.

The photoetch platelet concept is particularly well adapted to low costmass production techniques. Once the basic art work and negatives havebeen made, the manufacture of the platelets is a repetitive processrequiring little supervision. The quality control requirement is almostnon-existant as each platelet is a faithful reproduction of thephotographic negative. The assembly of the sequenced numbered plateletsis almost foolproof and can be rapidly accomplished by low-cost labor.The final assembled product is readily inspected by visual methods foracceptability.

These and other objects, features and advantages of the presentinvention will be more readily apparent from the following detaileddescription, wherein reference is made to the accompanying drawings, inwhich:

FIG. 1 is a cutaway perspective view of a preferred embodiment of thecarburetor according to the present invention when used with an externalcombustion engine;

FIG. 2 is an exploded perspective view, partially in cutaway, of one ofthe platelet assemblies of the apparatus depicted in FIG. 1; and

FIG. 3 is a phantom perspective view of one of the venturis of theapparatus depicted in FIG. 2.

Referring initially to FIG. I, there is depicted, generally at A, acarburetor or burner which, for purposes of illustration, is used withan external combustion engine. Carburetor A generally comprises acylindrical housing 10 having an end wall 12. End wall 12 includes acentral circular opening communicating with a cylindrical air inletpassage 14. The other end of housing 10 generally comprises the throatportion of the carburetor or burner A, and thus communicates with thecombustion chamber of an external combustion engine.

The present invention is widely applicable to external and internalcombustion engines of varying types. Typically, the throat of carburetorA may communicate directly with the combustion engine. Alternatively, aheat exchanger may be disposed adjacent the throat of carburetor A toextract the thermal energy of the combustion.

Disposed within housing adjacent end wall 12 is a multi-venturi assembly16 which functions to mix and vaporize fuel with the incoming air forcombustion. In the depicted embodiment, multi-venturi assembly 16 isgenerally tubular and is disposed coaxially and adjacent with inlet airpassage 14. Thus, incoming air is directed to the interior of thetubular multi-venturi assembly 16. As will be described in greaterdetail hereinafter, a plurality of venturi inlet ports 18 are formed onthe interior surface of multi-venturi assembly 16. Inlet ports 18communicate with a plurality of venturis which extend radially andterminate in a plurality of venturi exit ports 20 on the outer surfaceof the multi-venturi assembly 16.

Fuel is supplied to the venturis from an annular fuel manifold 28 whichcommunicates with a plurality of fuel passageways 26 interior ofmulti-venturi assembly 16. As will be described in greater detailhereinafter, the fuel is thus fed to the venturis where it is vaporizedand mixed with air. The vaporized fuel-air mixture exits from venturiexit ports 20 into the interior of housing 10 for combustion. This pathis generally shown by the arrows in FIG. 1. i

A secondary air inlet passage 30 is provided concentric with the bore ofmulti-venturi assembly 16 extending therebeyond into the interior ofhousing 10.

To achieve ignition of the fuel-air mixture, a threaded aperture 32receiving a spark plug 34 is provided on end wall 12 of housing 10. Apilot fuel passage 36 is provided between fuel manifold 28 and sparkplug 32 to insure an adequate supply of fuel at the spark plug forignition.

Referring now to FIG. 2, the construction of multiventuri assembly 16will now be described in greater detail. The multi-venturi assembly 16comprises an assembly or stack of platelets in the form of circulardiscs with central openings. Each row of venturis 24 generally comprisesa stack of four platelets. There is provided a first platelet 50 whichfunctions to distribute the fuel from the passages 26 to the venturis,second and fourth platelets 52 and 52 which form the upper and lowerventuri closures respectively and third platelet 54 which defines thebody of the venturi.

The platelets 50, 52, 54 and 52 may be considered as having angularsectors 56 which define a single venturi. Thus, the configuration of theplatelets will now be described in greater detail with reference to aparticular sector 56, it being expressly understood that the channelsand passageways to be described are repetitively formed in the varioussectors of the platelets to form a plurality of radially directedventuris in each stack 24 of four platelets.

Initially, it is to be noted that all of the platelets 50, 52, 54, and52 include, in each sector 56, a hole or aperture 26a. When theplatelets are assembled, apertures 26a align to define fuel passages 26directed axially with respect to the tubular multi-venturi assembly Fuelmetering platelet 50, as its name implies, functions to distribute andmeter fuel from the fuel passages 26 to the venturis. To this end, thereare provided through fuel metering platelet 50 a plurality of holes orapertures 60 aligned with the throats of the venturis. A channel orpassage 58 is provided on fuel metering platelet 50 communicatingbetween apertures 60 and 26a. In the embodiment depicted in FIG. 2, theventuri throats are angularly offset and radially inward from the fuelpassages 26. Thus, aperture is correspondingly radially and angularlyoffset from aperture 26a, and channel 58 traverses a J-shaped paththerebetween.

Venturi closure platelets 52 and 52' are mirror images forming the upperand lower venturi closure, respectively. Each of the venturi closureplatelets 52 and 52' include, in each sector 56, an aperture or hole 62disposed in registration with aperture 60 on fuel metering platelet 50.Thus, aperture 62 is disposed at the point of fuel introduction to theventuri, i.e. at the throat or at some desired point upstream thereof.The path of fuel to the venturi is thus through passage 26a, channel 58,aperature 60 and aperture 62.

Since venturi closure platelets 52 and 52' are provided on both sides ofthe venturi, it is apparent that fuel is introduced into the venturi atcorresponding locations on both sides thereof. To this end, the fuelmetering platelet 50 of the next adjacent row 24 feeds fuel to lowerventuri closure 52. It is thus apparent that each metering platelet 50feeds the bottom of the venturi above it and the top of the venturibelow it. Thus, such a second metering platelet S0 is depicted in FIG. 2below lower closure platelet 52'.

Venturi closure platelets 52 and 52 include, in each sector 56, aventuri shaped depression 63 which cooperates with venturi body platelet54 to define the venturi. Specifically, venturi body platelet 54generally comprises a plurality of radially directed fingers 64 havingventuri shaped spaces 66 therebetween. Spaces 66 are disposed inregistration with depressions 63, and thus cooperate to form the venturishaped passageway.

The platelets 50, 52, 54 and 52' are thus stacked in repeating sequenceuntil the required number of rows of venturis 24 have been formed. Therepetitive sequence of platelets may be offset circumferentially so thatthe venturi exit pattern for each row of venturis 24 may be staggeredvertically. This offset provides a more uniform injection pattern andface configuration. A blank closure platelet is provided at the bottomof the stack to complete the assembly.

The fastening of the platelets may be accomplished in numerous ways. Forapplications where minor leakage is of no great consequence anddifferential pressures are low, a simple, bolted assembly is adequate.This, of course, facilitates disassembly for servicing. An alternateapproach is the use of adhesives operable within the operatingtemperatures of the carburetor. Diffusion brazing is a feasiblealternative where leakage illimination is required and temperaturesprevent use of adhesives.

Referring now to FIG. 3, which is a phantom illustration of thepassageways associated with one venturi element, the venturi elementswill now be described in greater detail. As is apparent from FIG. 3,each venturi is substantially two-dimensional. The venturi is providedwith a small expansion angle to insure maximum pressure recovery,consistent with reasonable platelet length. The length of the diffuseris selected to maximize pressure recovery and to insure adequateresidence time for vaporization. The venturi height is based upon themaximum safe passage width permissible with assurance of flame quenchingto prevent flame flashback into the carburetor.

To summarize the operation of the venturi, with reference to FIG. 3, itis apparent that fuel from fuel passage 26 is conducted to the throat ofthe venturi via channel 58 and apertures 60 and 62. As describedhereinbefore, these passageways are duplicated on the opposite face ofthe venturi so that fuel is introduced into the venturi at correspondingpoints on the top and bottom thereof. The fuel can be either aspiratedinto the venturi by the difference in static pressure between theventuri and the fuel feed source, or it can be injected under pressure.Generally, aspiration of the fuel is preferred.

Air is forced into the venturi inlet 18 from the air supply or blower.The inleted air passes through the venturi restriction where it is mixedwith the fuel. The fuel-air mixture exits the venturi through venturiexit port 20. Since the venturis and the associated passages andorifices are substantially smaller than those found in conventionaldevices, smaller droplets, resulting in better vaporization, atomizationand mixing are produced.

What is claimed is:

1. A carburetor comprising: a housing having an air inlet and a fuelinlet, and a platelet stack in said housing defining a plurality ofventuris, said venturis being defined in planes parallel to theplatelets of said stack, said stack having a plurality of fuel passagesplacing said fuel inlet in fluid communication with respective venturis,said platelet stack being disposed with the inlets of said venturiscommunicating with said air inlet.

2. A carburetor comprising: a housing having an air inlet and a fuelinlet, and a tubular platelet stack in said housing defining a pluralityof venturis extending radially therethrough, said stack having aplurality of fuel passages placing said fuel inlet in fluidcommunication with respective venturis, said platelet stack beingdisposed with the inlets of said venturis communicating with said airinlet.

3. Apparatus according to claim 2, wherein said fuel passages areperpendicular to said platelets.

4. In a combustion engine carburetor having a housing provided with anair inlet and a fuel inlet, the improvement comprising: a platelet stackhaving a plurality of venturis defined therein and a plurality of fuelpassages adapted to place said fuel inlet in fluid communication withsaid venturis, said venturis being defined by venturi body plateletshaving a plurality of fingers defining venturi shaped spacestherebetween and pairs of venturi closure platelets respectivelydisposed on opposite faces of said venturi body platelets, said plateletstack adapted to be disposed in said housing with the inlets of saidventuris communicating with said air inlet.

5. Apparatus according to claim 4, wherein at least one of each of saidpairs of venturi closure platelets includes apertures respectivelyadjacent the throat of said venturis communicating with said fuelpassages.

6. A carburetor comprising: a housing having an air inlet and a fuelinlet and a stack of circular platelets having central circularapertures aligned to define a central tubular opening communicating withsaid air inlet, said stack having a plurality of venturis definedtherein directed substantially radially with the venturi inlets on saidcentral tubular opening, each of said platelets having apertures alignedin registration defining fuel passages communicating fuel from said fuelinlet to said venturis.

7. Apparatus according to claim 6, wherein said venturis are defined byventuri body platelets having a plurality of radially directed fingersdefining venturi shaped spaces therebetween and pairs of venturi closureplatelets respectively disposed on opposite faces of said venturi bodyplatelets.

8. Apparatus according to claim 7, wherein at least one of each of saidpairs of venturi closure platelets includes apertures respectivelyadjacent the throats of said venturis communicating with said fuelpassages.

9. In a combustion engine carburetor having a housing provided with anair inlet and a fuel inlet, the improvement comprising; a tubularplatelet stack having a plurality of venturis defined therein andextending radially therethrough and a plurality of fuel passages adaptedto place said fuel inlet in fluid communication with said venturis, saidplatelet stack adapted to be disposed in said housing with the inlets ofsaid venturis communicating with said air inlet.

10. Apparatus according to claim 9, wherein each venturi has a pair offuel passages communicating therewith on opposite sides thereof.

11. Apparatus according to claim 9, wherein each of said plateletsincludes apertures aligned in registration defining said fuel passages.

12. A carburetor comprising: a housing having an air inlet and a fuelinlet, and a platelet stack in said housing defining a plurality ofventuris, said venturis being defined by venturi body platelets having aplurality of fingers defining venturi shaped spaces therebetween andpairs of venturi closure platelets respectively disposed on oppositefaces of said venturi body platelets, said stack having a plurality offuel passages placing said fuel inlet in fluid communication withrespective venturis, said platelet stack being disposed with the inletsof said venturis communicating with said air inlet.

13. Apparatus according to claim 12, wherein said plurality of venturisare in substantial parallel orientation in said platelet stack.

14. Apparatus according to claim 12, wherein said platelet stack istubular and said venturis extends radially therethrough.

15. Apparatus according to claim 12, wherein the thickness of saidventuri body platelet is less than the flame quenching distance toprevent flame flashback into the platelet stack.

16. Apparatus according to claim 12, wherein at least one of each ofsaid pairs of venturi closure platelets includes apertures respectivelyadjacent the throats of said venturis communicating with said fuelpassages.

17. Apparatus according to claim 16, comprising a fuel metering plateletadjacent said at least one venturi closure platelet, said meteringplatelet including an aperture in registration with said aperture insaid venturi closure platelet and a channel connecting said aperture andsaid fuel passage.

18. Apparatus according to claim 17, wherein each of said plateletsinclude apertures aligned in registration defining said fuel passages.

1. A CARBURATOR COMPRISING: A HOUSING HAVING AN AIR INLET AND A FUELINLET, AND A PLATELET STACK IN SAID LOUSING DEFINING A PLURALITY OFVENTURIS, SAID VENTURIS BEING DEFINED IN PLANES PARALLEL TO THEPLATELETS OF SAID STACK, SAID STACK HAVING A PLURALITY OF FUEL PASSAGESPLACING SAID FUEL IN FLUID COMMUNICATION WITH RESPECTIVE VENTURIS, SAIDPLATELET STACK BEING DISPOSED WITH THE INLETS OF SAID VENTURISCOMMUNICATING WITH SAID AIR INLET.
 2. A carburetor comprising: a housinghaving an air inlet and a fuel inlet, and a tubular platelet stack insaid housing defining a plurality of venturis extending radiallytherethrough, said stack having a plurality of fuel passages placingsaid fuel inlet in fluid communication with respective venturis, saidplatelet stack being disposed with the inlets of said venturiscommunicating with said air inlet.
 3. Apparatus according to claim 2,wherein said fuel passages are perpendicular to said platelets.
 4. In acombustion engine carburetor having a housing provided with an air inletand a fuel inlet, the improvement comprising: a platelet stack having aplurality of venturis defined therein and a plurality of fuel passagesadapted to place said fuel inlet in fluid communication with saidventuris, said venturis being defined by venturi body platelets having aplurality of fingers defining venturi shaped spaces therebetween andpairs of venturi closure platelets respectively disposed on oppositefaces of said venturi body platelets, said platelet stack adapted to bedisposed in said housing with the inlets of said venturis communicatingwith said air inlet.
 5. Apparatus according to claim 4, wherein at leastone of each of said pairs of venturi closure platelets includesapertures respectively adjacent the throat of said venturiscommunicating with said fuel passages.
 6. A carburetor comprising: ahousing having an air inlet and a fuel inlet and a stack of circularplatelets having central circular apertures aligned to define a centraltubular opening communicating with said air inlet, said stack having aplurality of venturis defined therein directed substantially radiallywith the venturi inlets on said central tubular opening, each of saidplatelets having apertures aligned in registration defining fuelpassages communicating fuel from said fuel inlet to said venturis. 7.Apparatus according to claim 6, wherein said venturis are defined byventuri body platelets having a plurality of radially directed fingersdefining venturi shaped spaces therebetween and pairs of venturi closureplatelets respectively disposed on opposite faces of said venturi bodyplatelets.
 8. Apparatus according to claim 7, wherein at least one ofeach of said pairs of venturi closure platelets includes aperturesrespectively adjacent the throats of said venturis communicating withsaid fuel passages.
 9. In a combustion engine carburetor having ahousing provided with an air inlet and a fuel inlet, the improvementcomprising; a tubular platelet stack having a plurality of venturisdefined therein and extending radially therethrough and a plurality offuel passages adapted to place said fuel inlet in fluid communicationwith said venturis, said platelet stack adapted to be disposed in saidhousing with the inlets of said venturis communicating with said airinlet.
 10. Apparatus according to claim 9, wherein each venturi has apair of fuel passages communicating therewith on opposite sides thereof.11. Apparatus according to claim 9, wherein each of said plateletsincludes apertures aligned in registration defining said fuel passages.12. A carburetor comprising: a housing having an air inlet and a fuelinlet, and a platelet stack in said housing definIng a plurality ofventuris, said venturis being defined by venturi body platelets having aplurality of fingers defining venturi shaped spaces therebetween andpairs of venturi closure platelets respectively disposed on oppositefaces of said venturi body platelets, said stack having a plurality offuel passages placing said fuel inlet in fluid communication withrespective venturis, said platelet stack being disposed with the inletsof said venturis communicating with said air inlet.
 13. Apparatusaccording to claim 12, wherein said plurality of venturis are insubstantial parallel orientation in said platelet stack.
 14. Apparatusaccording to claim 12, wherein said platelet stack is tubular and saidventuris extends radially therethrough.
 15. Apparatus according to claim12, wherein the thickness of said venturi body platelet is less than theflame quenching distance to prevent flame flashback into the plateletstack.
 16. Apparatus according to claim 12, wherein at least one of eachof said pairs of venturi closure platelets includes aperturesrespectively adjacent the throats of said venturis communicating withsaid fuel passages.
 17. Apparatus according to claim 16, comprising afuel metering platelet adjacent said at least one venturi closureplatelet, said metering platelet including an aperture in registrationwith said aperture in said venturi closure platelet and a channelconnecting said aperture and said fuel passage.
 18. Apparatus accordingto claim 17, wherein each of said platelets include apertures aligned inregistration defining said fuel passages.